THE SOLAR SYSTEM| GEOGRAPHY FORM I: TOPIC 2
THE SOLAR SYSTEM
Solar system is the arrangement of planets and other objects in the space in relation to their position from the sun.
Components
Of Solar System.
Component of solar system include the
following:-
(a) Comets (b) Asteroids (c) Meteors
(d) Satellites (e) Stars (f) Sun
(g) Planets (h) interplanetary dust and gases
A. Comets
These are objects with leading heads and bright tails. Sometime at night, they are seen in the sky.
B. Asteroids
There are small bodies which revolve
around the sun. They are mostly found between the orbits of Mars and Jupiter.
C. Meteors
Is a piece of hard matter falling from space. They are seen as rapidly moving objects in the sky lasting for few seconds. When meteors fall on the Earth’s surface they are known as meteorites. Examples of fallen Meteorites in Tanzania are have been found at Malampaka in Kwimba District in Mwanza Region and at Mbozi District in Mbeya Region.
D. Satellites
Satellites are small bodies which
rotate on their axes and revolve around the sun. Satellites do not produce
their own light or heat but they shine at night by reflecting sun light
The
Satellite of the Earth
The earth has one Satellite called the
Moon. The moon is the natural
satellite of the Earth. The Moon rotates on its axis and revolves around the
Earth and it takes 29.5 days to complete one revolution. This period is called
the Lunar Month.
As the Moon revolve the Earth, the
distance between the two changes. When the moon is very close to the centre of
the Earth, it is called Perigee and
when the Moon is very far from the Centre of the Earth, it is called Apogee
The Moon is the nearest body to earth
hence appears larger than other bodies in the sky at night. The moon is spherical in shape with diameter
of 3480 kilometers. The distance of the moon from the Earth is at an average of
385,000 kilometers.
E. Star
A star is a body of hot gases seen as
a point of light at night. There are millions of stars in the universe. A
collection of stars is called a Constellation
F The
Sun
The sun is a star, it looks bigger than other
stars because it is closer to the earth. It is the only source of light for all
bodies in the solar system. The sun is the only body in the solar system that
generates its own heat and light.
Components Of The Sun
- Hydrogen
– 75%.
- Helium –
23%
- Other
elements – 2%.
Solar Energy
Solar energy is the energy from the
Sun. it is the energy, heat and light produced from the sun. Solar energy
reaches the earth`s surface in the form of ultra Violet, short wave radiation
and visible light
Uses
Of Solar Energy
- Solar
energy is used in the Generation of Electricity (called Solar
Power)
- used in
Drying; for example drying clothes, meat, fish and cerials/grains and so
on
- Source of
vitamin “D” to human body.
- Formation
of coal and oil.
- Used by
plants during Photosynthesis, i.e a process by which plants manufacture
their own food.
- Domestic
and industrial uses for different electronics like Calculators, torches,
watches, etc
- Used to provide
light and heat
Advantages
of Solar energy
- It is the
cheapest source of energy (not expensive)
- It safe
source of energy (has no danger)
- It is the
cleanest source of energy
- No
monthly charge when using solar energy
Solar
Energy and Conservation of the Environment
The use of solar energy can help to
conserve the environment in many ways such as:
- It
reduces the rate of deforestation; people will not cut tree for firewood
and charcoal
- It
reduces air pollution; the use of coal, diesel and firewood cause a lot of
air pollution
- It
reduces global warming by preventing bad gases going into the atmosphere
- It help
to keep our environment clean and safe
- Used in
photosynthesis hence reproduction of more vegetation
Solar
energy and Emancipation of Women in Africa
In Africa most women have a very big burden
of responsibilities in their societies. This makes them weak and marginalized.
So women must be saved/emancipated from such condition. There are many ways of
helping women, and one of them is the use of Solar Energy
The use of solar energy can emancipate
women in Africa in many ways as follow:
- It
reduces walking distance for women to find firewood
- It
reduces walking distance for women to fetch water
- It will
give girls more time for study and other activities
- It will
help to avoid raping of girls
- It will
help to avoid the illegal killing of women suspected of being witchcraft
just because they have red eyes (red eyes occur when women use firewood
for cooking)
- Women
will have more time to participate in economic activities
F. Planets.
- Planets are large bodies that revolve
around the sun. These planets revolve around the sun in anti-clockwise
direction in their obits.
- The path in the space which planet
follows as it revolves around the sun in called Orbit.
- The time taken to complete one revolution
depends on the distance of a planet from the sun. For instance Mercury being the
nearest planet to the sun takes short period of time to complete one revolution
compared to Pluto which is far from the sun.
- Planets which are near to the sun like Mercury
have short orbits than the planets which are far from the sun eg. Pluto.
The
nine known planets of the Solar System starting from the closest/nearest to the
sun are
1. Mercury 2. Venus 3. Earth 4. Mars 5. Jupiter
6. Saturn 7. Uranus 8. Neptune 9. Pluto
- The closest/nearest, Hottest
and the smallest Planet in the Solar System is Mercury
- The furthest and coldest
Planet in the solar system is Pluto
- The biggest/largest planet
is Jupiter
- The planet with Ring like
structure and with most satellites is Saturn
- The planet where life of
organisms is proven possible is Earth
All planets revolve around the Sun in the same direction in orbits that are elliptical and nearly in the same plane. The time taken to complete an orbit depends on the distance from the Sun.
Relative Distance of Planets from the Earth
How far is each planet from Earth?
Usually when people ask this question, what they mean is “What is the distance between the orbit of Earth and the orbit of each planet?” or “What is the closest that each planet comes to Earth?” (These are essentially the same question, because the planets can’t get any closer than their orbital spacing allows.)
You can compute this in a rough way by assuming that the orbits are circular and coplanar, and looking at the planet-to-Sun distance for each planet.
Since the distances are so large, we usually express them in Astronomical Units (AU). (AnAUis the average distance from Earth to the Sun, about 150 million kilometers or 93 million miles.) The table below lists the distance of each planet from the Sun in AU.
Planet | Average distance from Sun in AU |
| Mercury | 0.39 |
| Venus | 0.72 |
| Earth | 1.00 |
| Mars | 1.52 |
| Jupiter | 5.20 |
| Saturn | 9.58 |
| Uranus | 19.20 |
| Neptune | 30.05 |
| Pluto (dwarf planet) | 39.48 |
THE PLANET EARTH
The
earth is the third planet from the sun and the only planet of the solar system
proven/known to support life of organism.
Structure of the Earth
The
Earth`s structure is divided into two parts: the internal and external
structure
A The
external structure of the earth
The
earth`s external structure consists of the following:-
(i) Hydrosphere (water bodies)
(ii) Atmosphere (air)
(iii) Biosphere (living things)
B The
internal structure
The
earth`s internal structure consists of three concentric layers which are
(i)
The
crust; is the outer most part that consists of Sima and Sial
(ii)
The
Mantle; is the second layer that is made up of Olivine mineral
(iii)
The
Core; is the inner most part that consists of Iron and Nickel
Water bodies (oceans, lakes and
rivers) covers three quarter (¾) of the Earth’s surface while the remaining
part (one quarter) is covered by continents and Islands
The
Shape Of The Earth
The shape of the Earth is described as
spherical. It is not a perfect sphere but flattened at the Poles and Bulges at
the equator. The diameter through the equator is 12,757 km while the diameter
through the poles 12,713 km.
Evidence Of The Earth’s Shape
I. Aerial
photographs.
Photographs refer to a picture taken
by the Camera. Aerial photographs refer to a picture of objects taken by a
Camera fixed at a flying plane at a high altitude. These Aerial photographs
show that the Earth is spherical in shape.
II. Lunar
eclipse.
Lunar eclipse occurs when the Earth
passes between the sun and the moon. During lunar eclipse the shadow of the
earth is thrown on the moon. The thrown shadow is always circular or round in
shape.
III. Sunrise
and Sunset.
The fact that sun rises and sets from
place to place on the Earth’s surface proves that that the Earth is not flat.
People in East see the sun earlier than the people in West.
If the Earth were flat all places on
the Earth’s surface would have sunrise and sunset at the same time.
IV. Circumnavigation
of the Earth
If one travels across the world along
a straight path in a fast flying plane, he would come back to the same place
from where he started.
The first traveler around the word
named Magellan in 1519 – 1522 proved this when he completed his journey.
V. Ship’s
visibility
If one observes a ship coming towards
a port the smoke is seen first. As it comes closer to the Coast the Burrell
appears and finally the whole ship is seen.
This
gradual appearance of the ship proves that the earth is spherical in shape. If the earth were flat the whole ship would
have been seen at once.
Earths’ Movements
There
are two types of movements of the earth which are:-
a) Rotation
b) Revolution
A. Rotation
Rotation is spinning of a body on its
axis. The Earth rotates or spins on its axis in an anti-clockwise direction
from West to East through 3600 in 24 hours.
Evidence
To Prove Earth`s Rotation:
- During the night stars appears to move
across the sky from West to Earth.
- If one travels in a fast moving vehicle
will see trees and other objects on both sides of the road moving fast in the
opposite direction.
- Occurrence of day and night.
- Change of the length of the shadow. In
the morning
Effects
Of Earth Rotation:
- Deflection of winds and ocean current.
- The occurrence of tides in the oceans. A
Tide is the rise and fall of sea level
- Occurrence of day and night.
- Time differences between longitudes. It
causes the difference of one hour in every 150 interval between
longitudes.
B. Revolution.
Revolution means movement of one body
around another. The earth revolves the sun, taking 365¼ days to complete one
revolution. This period is called a Year
As the earth revolve the sun, the distance
between the two changes. When the earth is very near/close to the sun, it is
called Perihelion and the distance
is 147 Million kilometers, occurring
each year on 3rd January
When the earth is very far from the
sun, it is called Aphelion and the
distance is 152 Million kilometers
occurring on 4th July
Results Of Earth’s Revolution Around
The Sun.
A. Occurrence
of the Four Season of The Year.
Season is one of the distinct period
into which the year may be divided. There
are four seasons of the year, namely:-
- Summer
- Autumn
- Winter
- Spring
In Northern hemisphere,
(i) Summer months are - May, June and
July.
(ii) Autumn
months are - August, September and October.
(iii) Winter
months are - November, December and January.
(iv) Spring
months are - February, March and April.
In Southern hemisphere,
(i) Summer months are - November,
December and January.
(ii) Autumn
months are - February, March and April.
(iii) Winter
months are - May, June and July.
(iv) Spring months are - August, September and October.
Description Of The Diagram
The sun is over the equator twice a
year: On 23rd September and on 21st March
Equinox;
Means
equal day and night. Refers to the period when the sun is over head at equator
on 23rd September (autumn equinox) and on 21st March
(spring equinox).
.
The sun is overhead at Tropic of Cancer
on 21st June each year. This period is called Summer Solstice in Northern
Hemisphere or Winter Solstice in the Southern Hemisphere
The sun is overhead at tropic of
Capricorn on 22nd December each year. This period is
called Winter Solstice in the Northern Hemisphere
or Summer
Solstice
in Southern Hemisphere. Summer Solstice and Winter Solstice collectively are
called World Solstice.
B. Change in the position of Midday sun at
different times of the year.
C. Varying length of day and night at different
time of the year
D. Occurrence of Eclipse
ECLIPSE
Eclipse occurs when one body in space
is between two bodies of which one is a source of light. Eclipse can be partial
or Total. Total eclipse occurs when the entire moon or sun is hidden from view
and Partial eclipse occurs when a
part of moon or sun is hidden from view.
Types Of Eclipses.
There
are two (2) types of Eclipse which are:-
(a)
Lunar eclipse
(moon eclipse or an eclipse of the moon).
The Lunar
Eclipse occurs when the Earth passes between the Sun and the Moon. The earth
casts/throw its shadow over the moon
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Earth’s
orbit |
(b)The Solar Eclipse (Sun Eclipse or an
Eclipse of the Sun)
Solar eclipse
occurs when the moon passes between the Sun
and the Earth. In some parts of
Tanzania a total solar eclipse was observed on 23rd October, 1976.
Partial Solar eclipse occurred on 19th April, 1977.
Solar Eclipse
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LATITUDES AND LONGITUDES
Latitude
Is an angular distance of any point
measured in degree, minutes or seconds north or south of the equator. Latitudes
are imaginary lines drawn from West to East.
- Latitudes 00 is known as the Equator
- Equator is an imaginary line which
divides the earth into two equal parts called Hemisphere. Hemi means “Half”
thus hemisphere means half sphere. These parts are Northern hemisp here and
southern Hemisphere.
Important Latitudes
- Tropic
of Cancer 23½0
N.
- Tropic
of Capricorn 23½0
S.
- Arctic
Circle 66½0
N.
- Antarctic
Circle 66½0
S.
- The
North Pole 900
N
- The
South Pole 900
S
- Equator 00.
Diagram –
Important Latitudes
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Longitudes
Longitude is an angular distance of a
place measured in degrees East or West of the prime meridian. It is an
imaginary line running from North to South.
Prime meridian is line running from the poles through Greenwich near London. Therefore it is also called Greenwich Meridian.
Great
Circles
Great circle is a circle drawn in such
away that the centre of the circle is the centre of the Earth.
Characteristics
Of Great Circles.
- All great
circles divide the earth (sphere) into two equal parts (hemisphere)
- A great
circle is the largest circle that can be drawn in the surface of the
sphere.
- The
radius of great circle is the same as the radius of the earth.
Important Great Circles are
- All lines
of Longitudes
- Equator
- The Prime
Meridian/Greenwich Meridian
Importance
of great circle; used
to plot route ways for ship crossing high seas aircraft flying great distance
Time Zone
Is a stretch of land where standard
time is accepted throughout a longitudinal zone of 150 in width
Standard Time
Is a time agreed to be adopted by
different stretches of land from a certain meridian. For example East Africa
countries agreed to adopt time taken from the meridian 450 E.
Greenwich
Meridian Time (G.M.T)
This is the standard time for
Greenwich
The
International Date Line (IDL)
Is the line where date is changed or
calendar day begins. This follows on 1800 Meridian.
- It
is Zigzag at certain place to avoid confusion of one country to have two dates.
- It is also Zigzag to enable different
parts of the country to have the same date.
